1. Field of the Invention
The present invention relates to a die cushion drive system of a press machine, more particularly relates to a die cushion drive system powered by a servo motor.
2. Description of the Related Art
Oil pressure has been used as the source of drive power of a die cushion of a press machine in the related art.
FIG. 5 is a side view showing the configuration of a die cushion drive system of a press machine of the related art. In the figure, 51 indicates a slide moving vertically to press sheet metal or another worked object (not shown), 52 a die cushion for applying pressure upward to the worked object, 53 a motor for driving the slide 51, 54 a mechanism for converting the rotational energy of the motor to energy of vertical motion, 55 an arm for giving this vertical motion energy to the slide 51, 56 an oil pressure cylinder, 57 an oil pressure pipe, and 58 an oil pressure apparatus.
At the time of power operation, the energy from the motor 53 is used to make the slide 51 move downward and oil is transmitted from the oil pressure apparatus 58 through the oil pressure pipe 57 to the oil pressure cylinder 56, whereby the die cushion 52 is pushed upward and the worked object is worked.
In the above oil pressure type die cushion drive system of the related art, when the force from the slide 51 to the die cushion 52 is higher than the force from the die cushion 52 to the slide 51, energy is transmitted in the direction of the illustrated bold arrows and radiated from the oil pressure apparatus 58 as heat, so there was the problem that energy was wastefully consumed.